COLIN WONFOR: MP/MF330 pre power pair problem

Colin Wonfor

I recently sourced my friend his fab MP/MF330 pre power pair. I was listening to them through his ES14s and could hear a hiss on both channels (slightly more on the right). You need to stick your ear to the speaker, and turning the un-fed pre volume right up didn't change it too much. This pre-power pair is, I suspect, around 15 years old, and could perhaps benefit from a service at some stage. I was wondering if there was a bias set up procedure for the MF330 power amp, please? The combo still sounds great - really nice kit - but it would be nice to fettle them into inky silence if possible. Many thanks for your thoughts. Might be a later design, but I think it is based on your original work.

I am sorry to say I was not with Magnum when these amps were hatched. Now if Tony used the original designs – as I suspect he did over and over – then are your power amps hissing without the pre-amp? If yes then check PSU ripple. If no then I suspect a cap has gone in the A Class output stage of the pre. Contact Paul Quick (Quickie is on Audiochews) he fixes them and does a truly wonderful job.

Colin